ClassPass can only book Primary spots. If there is a secondary spot open, it will never be able to be booked in ClassPass.
If you want to make it so ClassPass reservations are reserved to the floor first, you will need to create the layout to have the floor spots created first, then treadmill spots. Otherwise, it will be random. These layouts cannot be duplicated and must be made for every single class in order to avoid ClassPass users always going to the same spots
ClassPass users are assigned a PRIMARY spot at random based on the way that the layout was created.